Although digital data networks have existed for many years, an important use of such networks that has risen in popularity recently is the transmission of voice traffic. Such networks employ a “packet-switched” connection, whereby voice signals are broken down into discrete portions, or “packets,” which are transported across the network to the appropriate destination, where the packets are then reassembled. As a result, unlike a standard telephone “circuit-switched” network, whereby an entire physical connection must be maintained between the parties of a one-on-one conversation for the duration of a phone call, digital data networks are not required to maintain such a complete physical connection at any point during the conversation. Each of the packets traversing such a network during a conversation can safely arrive at its destination without all of the packets being required to travel along an identical route in a contiguous fashion. Thus, data networks allow greater flexibility in establishing and maintaining voice connections than standard analog phone networks.
Use of a digital data network for voice communications also allows bandwidth to be saved in a way not available to analog phone networks. Voice calls typically include a significant amount of time when little or no useful audio information is being transmitted. By not transmitting packets during these times, a digital data network can save communication bandwidth that would otherwise be allocated to that call, thus allowing more such calls to be handled by the network at any one time.
On the other hand, dividing a voice transmission into packets also introduces potential problems that are nonexistent in circuit-switched systems. For example, since the packets are being transmitted over a digital network, the original analog voice signal must be converted into a digital data format, and then converted back to an analog signal prior to being received by the listener. Such transformations can possibly degrade the original signal in ways not encountered over an analog, circuit-switched network. Also, due to the nature of the interfacing circuitry between the digital network and the analog portions of the communication path, an unwanted “echo” of the voice signal may be generated. Furthermore, considering that the entire communication path is not allocated end-to-end for the duration of the conversation, “latency,” or source-to-destination delay, may be encountered. Additionally, in periods of heavy traffic in the data network, occasional interruptions in the delivery of the voice signal to the destination may also occur. Any of these problems could cause a noticeable decrease in the quality of service expected by most customers.
Given the types of problems that may occur with the transmission of voice signals over digital data networks, proper testing of such networks with respect to voice signals is vital. Many types of electronic equipment exist that test various aspects of communication, including both analog voice and digital data transmissions. Likewise, with the fairly recent advent of voice transmission over digital networks, some voice quality test systems have been devised. Some of these test systems are capable of executing complex testing algorithms to measure various aspects of the voice quality delivered by a packet-switched digital data network. Many of these systems are necessarily expensive, requiring a PC-like interface, possibly including monitor and keyboard devices, to allow the test system user to control the testing process.
To fully test a voice call over a digital data network, tests should be performed on calls that are initiated from either end of the connection. Tests performed in this manner are important since the path that voice packets travel through a data network is often determined in part by the location of the origination of the call. Since different paths can yield different voice quality measurements, the ability to initiate calls in either direction is crucial to duplicating “real-world” conditions. Currently, to perform such tests, two test systems, with a human operator directly controlling each system, must be involved in the test (one at each end of the communication path being tested), resulting in a costly and cumbersome solution.
Thus, it would be advantageous to perform thorough voice quality testing over digital data networks without having to utilize two test systems that both require local test operator intervention. Additionally, it would be a benefit to be able to perform such testing over phone connections, neither end of which is occupied by an operator, allowing testing of connections that are completely remote from the human test system operator.